TITLE: GCN CIRCULAR NUMBER: 35780 SUBJECT: GRB 240222A: Swift-XRT refined Analysis DATE: 24/02/23 01:05:15 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> A.P. Beardmore (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 240222A, from 106 s to 41.2 ks after the BAT trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 143.2254, -68.0305 which is equivalent to: RA (J2000): 09 32 54.10 Dec(J2000): -68 01 49.7 with an uncertainty of 3.5 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=2.02 (+0.12, -0.11). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.52 (+0.24, -0.12). The best-fitting absorption column is consistent with the Galactic value of 1.7 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.6 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.7 (+/-0.9) x 10^21 cm^-2 Galactic foreground: 1.7 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.52 (+0.24, -0.12) If the light curve continues to decay with a power-law decay index of 2.02, the count rate at T+24 hours will be 1.3 x 10^-5 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x 10^-16 (6.7 x 10^-16) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01216804. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/35780. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...